The present invention generally relates to the textile industry. More specifically, the present invention relates to the bonding of garments with elastomer and a method of production.
Since old ages, sewing garments was done with needles and threads. Conventionally, to hem a piece of cloth, a garment worker folds up a cut edge, folds it up again, and then sews it down. The process of hemming thus completely encloses the cut edge in cloth, so that it cannot ravel. Hems are used in order to tidy the edge of the fabric, where it was cut. The hem prevents the cut edge to become further separated, and provides a strong, neat and straight edge. The hem may be sewn down with a line of invisible hem-stitch or blind-stitch or sewn down by a sewing machine, usually leaving a visible line of sewing. Machines can also sew a reasonable facsimile of a hem-stitch, though the stitches will usually be larger and more visible. Most haute couture hems are sewn by hand for this reason.
Attention is now directed to FIG. 1a, which illustrate the production of a typical panty leg hole. The panty starts as a cylindrical piece of cloth 101. Cutting on lines 102a-b and sewing together the front and back at seam 104 (see FIG. 1b) produces Leg holes 103a-b. Then an elastic band is set around leg holes 103a-b and a hem is folded over the elastic band and sewn down. For easy dressing it is preferable that leg holes 103a-b can stretch to at least 180% of their unstressed circumference. For comfortable wearing it is desirable that back seams 105a-b of leg holes 103a-b can stretch without noticeable force to at least 125% of their unstressed length and that top front seams 106a-b of leg holes 103a-b can stretch without noticeable force to at least 110% of their unstressed length. Bottom front seams 107a-b of leg holes 103a-b do not need to stretch appreciably during wearing. In order to enable stretching of leg holes 103a-b it is necessary to gather material around the elastic band along the seam because the fabric of panties is not as elastic as the rubber band. For comfortable wearing and minimal seam thickness, the accumulation of material on back seams 105a-b should be more than the accumulation on top front seams 106a-b, which should be more than the accumulation on bottom front seam 107a-b. Another important demand is that after such stretching the seam will return to its original length almost immediately (short recovery time).
Often, as described in connection to FIG. 1b, especially in underwear, to make better closures, an elastic band is sewn on the hem. For example, synthetic panties generally have a cotton lined crotch and elastic band that form a full leg closure. Typically in the prior art (for example U.S. Pat. No. 5,203,268 to Schips), the elastic garment products are made with a single piece of elastic or two pieces, which are undulated. The stiff elastic stretched to a desired length serves as a form to ensure that the hem is straight and that (when the elastic returns to its un-stressed length) the material will have enough gathers to allow stretching of the seam.
Unfortunately, the elastic band increases the garment thickness in the hem region. The thick area can be seen and felt through the outer garment, resulting in reduced the wearing comfort and undesirable panty lines. Another problem is durability the rubber band. After a few washing cycles conventional rubber bands wear off or deteriorate and do not return to their original length.
Furthermore, conventionally sewing of an elastic band into a hem requires a multi-step process (starting of a subsequent step only after completing the previous step).
These are the three steps of the current conventional sewing process:                1. Cutting the entire length of the material.        2. Inserting the elastic band while stretching the elastic band to the desired length and fixing it to the garment (usually by local stitching).        3. Folding the material around the elastic band and sewing down the fold.        
This three-step process of inserting an elastic band demands time and labor in the manufacturing process, and increases the cost of producing the garment.
The textile industry is looking for a solution to speed production of hems and particularly of elastic hems and to reduce the thickness of hems in underwear, especially in lingerie. In the industry's jargon, the solution is called “seamless”; sometimes it is also referred to as “stitchless” technology. Several attempts have been made to provide the production of underwear without the visible panty lines; however none have adequately provided a solution. For example, U.S. Pat. No. 6,681,407 to Christine Martz discloses a women's waistless and seamless clothing adherable underwear that includes an oval pad made of a soft absorbent material. The pad has strips of adhesive tape to attach to the inside crotch area of low slung clothing pants or tight pants. The problem with Martz is that the adhesive can pull away from the clothing if not secured properly. Moreover, due to the cost of the elastic band, this kind of solution is not always desirable.
Over the years, numerous techniques have been developed to taking advantage of the properties of elastomeric materials for bonding textiles.
Most elastomers are monomers that are applied in an uncured state. After curing (e.g. polymerization) the elastomer becomes an elastomeric rubbery type of solid at room temperature. While uncured, the elastomer (referred to hereafter as adhesive) is applied to the region to be bonded. The elastomer penetrates into the fabrics and cures. The elastomer may be used to bond the fabrics together, and still allow flexibility and elasticity. Under certain conditions, the cured elastomer may serve as a replacement for an elastic strip or rubber band. Thus, by incorporating an elastomer into a garment, a “built-in” elastic strip is produced. The hem of a “built in elastic strip” is much thinner than a hem including a pre-formed elastic strip sewn into the clothes. Hence a garment incorporating a thin elastomer closure may be described as “seamless”. Furthermore, use of pre-formed elastic strips incurs extra manufacturing costs associated with the cost of the pre-formed band and the time and the work needed to sew the pre-formed band into the garment.
Conventionally, to create an elastic hem with an elastomer, a prefabricated elastomer band is inserted into the hem. The garment is then ironed to heat the band, melting the elastomer. Pressing the two fabrics together with the elastomer in-between, establishes the bond. Such prefabricated bands of elastomer are available from BEMIS Associates, Inc. (One Bemis Way, Shirley, Mass. 01464, USA) and are usually made of polyurethane. Unfortunately, this method has many disadvantages: first of all, the prefabricated bands are expensive; secondly, during the process the heat has to reach the band through the surrounding fabrics, the process is therefore very slow compared to sewing. To overcome this shortcoming, the power of the heat source may be increased, but increasing the power of the heat source entails a risk of burning the garment. Another disadvantage of this method is that polyurethanes have a long recovery time. The term “recovery time” refers hereinafter to the time needed for the elastomer to reach its initial length after been stretched. Polyurethanes take about a minute or more to recover.
Yet another common way to bond hems, typically in outer garments like dresses and trousers, is to spread fine particles of material, usually known as hot melt adhesive, inside the hem. The hem is then ironed, melting the particles, which become “bonding points” holding the hem. This method is not adequate for undergarments, where hems are very narrow, about 5 mm. It is also not used as a replacement for elastic strip, since the particles are not continuous. Therefore no continuous elastic band and no elasticity are formed. Only the region of the particle is bonded.
Despite all of the efforts that have been made to provide a facile, economical process for mass production of conformable garments, problems have, prior to the advent of the present invention, continued to plague the industry. In addition to many of the problems described above, many of the thermoplastic elastomeric materials that have been suggested present similar, as well as somewhat different problems. For example, since the elastic material is here contemplated for usage in garments, it is important that the material be characterized by its strength; not only strength in usage, but also in the high speed manufacturing processes employed. It is also important that the heated material possess sufficient strength as to resist breakage, particularly when the heated material is being worked on in a high-speed continuous production process. There is thus an unfulfilled need for selecting suitable elastomers overcoming the shortcomings described above.
Moreover, there is an unfulfilled need for providing a cost effective method to integrate an elastic strip into a garment.